Hi, Emma!
Welcome back to the Disney Parks Moms Panel, and thanks for your great question! I’m glad to hear your family is planning to visit the Disneyland Resort together soon.
The Baby Care Centers are a great resource for families with babies and toddlers, and there’s one located in each of the theme parks—near the end of Main Street, U.S.A. next to First Aid in Disneyland Park and next to Ghirardelli Soda Fountain and Chocolate Shop in the Pacific Wharf section of Disney California Adventure Park. In addition to a comfortable, private place to nurse her child, your sister will find a variety of amenities that make parents’ lives much easier. There are full-size changing tables, high chairs, a kitchen and a shop with baby food, formula, bottles, pacifiers, diapers, wipes, medicines and other essentials for purchase.
Keep in mind that there are lots of attractions your whole family, including your sister’s little one, can ride together at both parks, including Dumbo the Flying Elephant, “it’s a small world,” Mickey’s Fun Wheel, Monsters Inc. Mike & Sully to the Rescue!, and The Little Mermaid - Ariel's Undersea Adventure, just to name a handful. If it is labeled as being suitable for "any height” or there is not a minimum height requirement posted at an attraction, then even a baby may ride.
I hope this helps, Emma, and that you have a wonderfully pixie-dusted visit to the Disneyland Resort! Please write back with any other questions you have as you continue to plan. I’d love to hear from you again.
Wishing you magic,
Courtney